Photomechanical negative



Jan. 18, 1944. a. 'RuDNlcK PHOTOMECHANICAIJ NEGATIVE original Fned nay21. i941 INVENTOR. efgm Rua/mbk BY 7L twwy.

Reissued Jan. 18, 1944 PHOTOMECHANICAL NEGATIVE manier, jHuntington. N.Y., man to Republic Aviation Corporation, Farmingdale,

, N. Y., a corporation o! Delaware Original No. 2,321,046, dated June 8,1943, Serial No. 418,435, November 10, 1941, which is a division o!Serial No. 394,403, May 21, 1941. Application for reissue ctober z,1943, Serial No.

505,561 8 Claims.

This invention relates to the preparation of a photo-mechanical negativeto be used for the photo mechanical sheets, mechanical layouts,templates, etc.`

The invention aims to provide a photo-me-` chanical negative which canbe used in connection with the method of reproduction disclosed in myco-pending application, Serial No. 394,403, filed May 21, 1941, of whichthe present application is a division.

More particularly the invention aims to provide a negative forreproduction by which inscriptions, for example, line drawings,luminescently produced upon the negative may be transferred to anothersurface, which has previously been rendered light-sensitive bymomentarily placing the two surfaces in contact with each other to causeexposure of the sensitized surface by the luminescent inscriptions.

According to one of the preferred modes of carrying out this method, astiff backing sheet or plate is coated with a layer of luminescentmaterial having an overcoating of opaque masking material, the layers ofluminescent and masking materials constituting what, foriconvenience, Iterm a negative surface. The copy lsheet to which the design is to betransferred is coated with a film of light-sensitive emulsion so 'as toform what may be referred to as a positive surface. The drawing to bereproduced is made uponthe'negative` surface by means of a stylus orother pointed instrument which cuts or scratches through the overcoatingof opaque masking material, and uncovers the luminescent material. Afterpresenting the negative surface to a vbright light, either natural orartificial, to excite the uncovered luminescent material, the treatedsurfaces are superimposed to allow the light rays emitted by theuncovered luminescent material to act upon the light-sensitive film.Finally the copy sheet is developed and fixed in the usual photographicsolutions to reduce the exposed areas to visible metallic silver,leaving these areas black and clear-cut, and corresponding exactly tothe lines of the original drawing.

'I'he use of this negative is not limited to this method of reproductionof drawings upon sheet material, and will indeed find great 'utility inmachine and sheet metal shop practice inl transferring mechanicallayouts or templates as they reproduction of drawingv photo-mechanicalnegative on which any kind of l line drawings may be readily marked,corrected or completed by means of a stylus sol as to form a masterpattern which may be repeatedly used for the preparation of new drawingsor the localized correction of old drawings.

Other objects and advantages will be apparent from the followingdetailed description of two preferred modes of realization of myinvention, reference being had to the annexed drawing in which:

Figures 1 to 4 refer to the rst mode;

Figure l is a plan View of a negative or pattern sheet having a drawinginscribed thereon; Figure 2 is a cross-sectional view of the patternsheet taken on the line 2-2 of Figure 1, the coating layers being shown,'for greater clearness, somewhat exaggerated in thickness;

Figure 3 `is a cross-sectional view of a copy sheet, which is preferablyused in combination l with this negative according to the method ofreproduction disclosed in the above-mentioned zzo-pending application,and

Figure 4 indicates the manner in which the negative and this copy sheetare arranged during their exposure.

. Figures 5 and 6 are views similar to Figures 2 and 4 respectively ofthe second mode; and

Figure 7 shows 'a different manner in which the negative and the copysheet may be arranged during their exposure.

In Figures 1 and 2 of the drawing is illustrated a photo-mechanicalnegative or pattern sheet A comprising a backing sheet I, which may becomposed of paper, cardboard, metal, or any other suitable material. Onesurface of the backing sheet is thoroughly cleaned to free it from dirt,grease, or oil, following which a thin coating of white paint 2,containing no lead compounds, is applied over the surface, Upon thecoating of white paint is deposited, either by a spray or a brush, alayer of a luminescent composition 3- susper'ided in a transparentvehicle. For this luminescent composition I prefer to use the reactionproduct resulting from igniting a mixture After allowing the luminescentcomposition to dry so that it is no longer tacky but firm and hard,

a thin coating of opaque masking material I is evenly distributed overits surface, s o as to completelyl cover the luminescent layer. Thismask- `ing material may comprise a black lacquer such as is compatiblewith the lacquer vehicle containing the luminescent composition. ,l

The layerof luminescent material overlain by 4the coating of maskingmaterial constitutes a' negative surface upon which, after drying, adrawing 5 may be inscribed by means of a stylus or other pointedinstrument, whichcuts through the overcoating of masking materialy andbares the luminescent composition underneath. Be-

cause of the fact that the masking material adheres as an extremely thincoating to the lumily and clean-cut against the black background of themasking material. 'Should the drattsman make a mistake in initiallylaying out the drawing, this may be readily corrected by painting over,and thus blacking out the incorrectly placed lines with a black lacquercorresponding in composition to that of the masking material, thecorrect lines afterwards being added whenA the lacquer has dried.

placed upon a flat, solid support in a dark room,

treated `face up, andthe copy sheet is superimposed iipon the patternsheet with its treated face heldrmly in engagement with the treated faceof thepattern sheet to insure absolute contact therebetween. Under suchconditions, the

` light rays emitted by the uncovered luminescent composition actphotographically upon the lightsensitive emulsion and cause the silversalts to be y sufliciently aected usually in about one and one-half totwo minutes. The thus-exposed copy sheet is finally removedand treatedwith the usual developing and fixing solutions in a manner which iswell-known to the photographic art, and then washed and dried. Becausethe negative surface retains its luminescence for a considerable time, agreat number of copies of the The thus-prepared sheetis now placed in avstrong light, which lmay be either naturalsunlight or artificial light,for example, ultra-violet light, the purpose of which is to excite theluminescent composition uncovered by the stylus so that it gives oifradiations in a dark room. Only a few minutes is required for suchexcitation, following which the pattern sheet is ready 'for use as amaster negative from which reproductions of the drawing may bephotographically transferred to copy sheets, one of such copy sheetsdesignated B, being shown in cross-section in Figure 3.

The copy sheet B comprises a backing sheet 6 of metal, fabric, paper,glass, synthetic plastic, wood, or any other suitable material, or itmay constitute the 'actual work to be operated upon. One face of thebacking sheet is cleaned. A coating of priming material 1 is thenpainted or `sprayed over the cleaned surface, the primer serving both asa filler for closing the pores of the material composing the backingsheet, and as a protective shield between the backing sheet and theemulsion which is subsequently applied thereto, and which otherwisemight interact chemically with the backing material. I prefer to use asthe primer a suspension of zinc c'hro'-V mate in a carrier selected withconsideration to drawing may be reproduced therefrom in a single darkroom operation; and when its luminosity becomes spent it can be restoredby again presenting it to a strong light.-

The drawing reproduced upon the copy sheet exhibits black,sharply-defined lines against the olive-green background of the primercoating, which is pleasing and restful to the eyes. If desired, however,the olive-green color may be bleached out to reveal the color of thebacking sheet 6, by immersing the copy sheet in a dilute solution ofammonium hydroxide; or the copy sheet mayL be rendered transparent ifglass or a Y ltransparent plastic is employed as the backing material.

If an aluminum alloy is used as the backing of the copy sheet, thelight-sensitive emulsion canbe applied directly on the metal by firstclean-- ing the surface in a sodium hydroxide solution a templatecorresponding to the contour of the the nature of the material composingthe backing sheet. When the backing sheet is composed of a metal such assteel, both of its faces, as well as its edges, will be covered ,withthe primer to avoid contamination of the chemicals employed in thesubsequent developing operation.

`The copy sheet is next placed in a dark room illuminated, for example,by a ruby safelight of the type well known to photography; thetemperature is maintained substantially constant and` an emulsion I,consisting for example, of a light-sensitive material, such as silvernitrate suspended in a gelatinous vehicle, is melted and applied as aillm in any suitable manner giving an even thickness, though I prefer toapplyit original drawing is obtained. l

Manifestly, the .negative described above is susceptible ofmodification. While I have found that a luminescent compositionincorporating the reaction product of burned calcium carbonate andsulphur, as above-described, gives excellenti results ybesides beingcomparatively inexpensive toproduce, nevertheless other compositions maybe advantageously employed such, for example. as the phosphoruscompounds. The coating of white. paint 2 upon the pattern sheet may beomitted if desired, and the luminescent material applied directly to thebacking sheet I. However, the ypresence of this white substratumadvantageously affects the results obtained, particularly in those caseswhere the layers of luminescent material is relativelythin, or where thecharacter of the backing material is such as to absorb rather than toreect transmitted light.

vThe pattern sheet may be repeatedly used for the preparation of new orcorrected drawings simply by completely or partially blacking over itsinscribed surface with a fresh coating of black lacquer. After thelacquer has dried, a new and different drawing, or a localizedcorrection of an old drawing, may be, inscribed upon the renewedsurface, the procedure being otherwise the same as that described above.

Another mode of preparing a negative C which can be used to reproduceonto the same light-sensitive coated copy -sheets as are used in theluminous mode may be carried out in the following manner (Figures to 7):a clear plastic sheet .01 to .015 thick is seated with an opaque maskingmaterial consisting of two separate layers l0. Il of a metallic lacquer.metallic lacquer are `so applied that they can be scribed off or cutaway, without scratching or cutting into the plastic backing sheet 9.The iirst coating I0 is prepared by mixing a quantity of iinely groundaluminum powder in nitro-cellulose lacquer to form a thick paste. Thisis thinned with a mixture of solvents to a suitable consistency and isapplied to the surface of the plastic sheet 9. This coating I0, whendry, renders the plastic material 9 opaque but can readily be removedwith a few strokes of a still brush. The material for the second coatingIl is prepared by mixing a quantity of metallic powder, which consistsmainly of tin, to a greater amount of nitro-cellulose lacquer thanWas-used in the iirst coating I0. To this is added enough solvents tothin to the desired consistency and this is applied over the rst layerI0. drying, the second coating II acts as a. binder for ,the rst coatingI0. The drawing to be reproduced (not shown) is drawn on this surface bymeans of a pointed instrument which cuts or removes the top layer Il ofmasking material These layers of of a luminescent composition supportedupon said y backing member. and a coating of an opaque masking materialoverlying said layer of lumi-y nescent composition, said maskingmaterial being of a thickness and composition lsuch as to be readilypenetrable by a stylus.

2. Photo-mechanical negative for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member comprising the reaction product resulting from burning amixture ,of calcium carbonate and sulphur suspended in a resinousvehicle, and a coating of an opaque masking material overlying said4layer of luminescent composition; said maskingvmaterial being of athickness and composition such as to be readily penetrable by a stylus.

3. Photo-mechanical negative for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member comprising the Lreaction product resulting from burning amixture of calcium carbonate afnd sulphur together with a relativelysmall amount of a bismuth salt suspended in a resinous vehicle, and acoating of an opaque masking material overlying said layer ofluminescent composition, said masking material being of a thickness andcomposition such as to be readily penetrable by a stylus.

making it possible to brush out the aluminum powder Il) underneath,covering the transparent plastic backing 9.` This is now used as aphotographic negative C. It' is, for instance, placed in. contact withthe light-sensitive copy sheet 6, l, 8 and exposed to artificial lightfor a predetermined time. 'I'hese light rays pass through thetransparent portions of the plastic negative C, reacting on thelight-sensitive salts of the copy sheet B. The exposed copy sheet B isthen processed in the usual photographic solutions. The resultingreproduction appears as a sharply defined black line on a cleancontrasting background.

An outstanding advantage in the use of the plastic negative is the factthat leither a right hand or left hand reproduction can be obtainedaccurately by merely placing the coated surface of the plastic negativeC (to produce a copy in reverse of the design as drawn) in directcontact with the light-sensitive copy plate B (as shown in Figure 6) orby placing the back or uncoated surface of the plastic negative in'contactwith the light-sensitive copy plate (as shown -n Figure '7).

4. Photo-mechanical negativey for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member comprising the reaction product resulting from burning amixture of calcium carbonate andsulphur together with a relatively smallamount of a manganese salt suspe'nded in a resinous vehicle, and acoating oi an opaque masking material overlying said layer ofluminescent composition, said masking material being of a thickness andcomposition such as to be readily penetrable by a stylus.

5. Photo-mechanical negative for reproducing 'designs comprising abacking. member, a layer of a luminescent composition supported uponsaid backing member comprising the reaction product'resulting fromburning a mixture of calcium carbonate and sulphur suspended in anitrocellulose lacquer vehicle, and a coating of black lacquer overlyingsaid layer of luminescent composition, said black lacquer being of athickness such as to be readily penetrable by a stylus.

6. Photo-mechanical negative for reproducing I designscomprising abacking sheet one face of which is thoroughly cleaned, a thin coating.of white paint applied upon this cleaned face, a layer of a luminescentcomposition suspended in a transparent vehicle spread and dried uponthis coating of white paint and a thin coating of an opaque maskingmaterial evenly distributed over the surface of this layer ofluminescent composition.

7. A photo-mechanical negative for the reproduction of designscomprising a substantially smooth opaque backing member, and a designdelineated in an inherently actinic ray emitting material adhered to thebacking member.

8. A photo-mechanical negative for the reproduction of designscomprising a substantially smooth opaque backing member, and a designdelineated in light-responsive, actinic ray emitting material adhered tothe backing member.

BENJAMIN RUDNICK.

